Various electronic power counters are known for the purposes of current collection, which are increasingly replacing the mechanical Ferraris disc meter in industrial as well as household usage, and carry out the current collection with differently structured order structures. Along with current collection with mess shunts, Rogowski solenoids or Hall elements, current transformers based on soft magnetic ring cores, in particular ring band cores as magnetic modules in electronic counters are also widely used. A magnetic module (current transformer, transformers) causes a galvanic network separation and delivers a precise measurement size in the form of a signal voltage at a load resistor. The requirements of exactness of amplitude, exactness of phases and linearity are fixed through IEC 62053, -21, -23 and/or earlier 1036 in Europe as well as ANSI C12.xx in the USA, and are to be found for example in the prospectus of the firm “VAC current transformers for electronic energy meters”, of the vacuum smelter, Oct. 1998. Current transformers for electronic energy meters are generally also well known from the prospectus of the firm “Current transformers for electronic energy meters” of the vacuum smelter, 2002. Such energy meters using current transformers (also known as watt-hour meters) serve as officially authorized means of measurement, in order to settle the cost of the electric current used by a consumer vis-à-vis the energy providing concern.
Well known are a structure of current bars and a ring core current transformer corresponding to it for the collection of consumer electricity consumption in energy meters. In pluggable electricity meters widespread in the USA and other countries there are standardized rectangular terminal lugs on the reverse, which are plugged into plug points with corresponding spring contacts at the time of assembly of the electricity meter. These lugs with a cross-section of approx. a×2.5 mm serve to supply and discharge the consumer current, which amounts in the 110 V systems to a maximum of approx. 200-480 Aeff. As thickness ‘a’ of the cross-section for example a=19 mm is set at a maximum current of I-max=320 A. Normally the currents of the three phases of the alternating current network are directed into the electricity meter, taken through by a current collection system and out again from the electricity meter. An electronic circuit in the electricity meter collects the currents of the three current collection systems and calculates the energy consumed from the strength of the current and the position of the phase, as is for example known from U.S. Pat. No. 4,887,028.
The most economical manufacture at present of a magnetic component for high output current transformers exists in the manufacture of ring cores, in particular in ring band cores, and the winding of the isolated and/or encapsulated cores with the corresponding secondary winding based on magnet wire. Suitable cores are known for example from the EP 1 131 830 and EP 1 129 459. WP 1 114 429 describes current transformers for such purposes.
One possibility of the constructive structure of a current transformer exists in that the size of the current transformer is so chosen that it is possible to insert a current bar of, for example, the size of 19×2.5 mm right through the inner bore of the current transformer.
An optimizing exists in that the area of the current bars, on which the current transformer is to be placed, is given a round cross-section. In this manner the inner bore of the current transformer can become smaller, and as a consequence of this a smaller ring band core can be used, whereby this is then, determined by the method employed, correspondingly more economical. Even if the same use is made of soft magnetic band material and with the same winding time for the core, the steps of the process of a heat treatment and a layering are more economical, the smaller the diameter of the core. The manufacture of a current bar suitable for this takes place through the provision of a U-formed conductor structure with various line sections. A central constituent section of the circuit with a round cross-section serves as the element of the current transformer for insertion in the corresponding opening in the core. Two line connections with rectangular cross-sections serve to connect the conductors in the form of well-known plug-and-socket connections. The order structure of conductors thus consists of three metal parts with cross-sections at variance with each other, whereby both the ends of the round conductor are to be fixed to the flattened surfaces of the rectangular line connections.
Well known for the purposes of fixing is the connection by means of resistance point welding or hard soldering. Both methods require however costly and elaborate method technology as well as a high degree of application of energy for each of the connection points to be made. A particular difficulty is to be seen in the checking of the connection points, carried out simultaneously with the installation process, for the purposes of ensuring the quality of the order structure of the conductors, since the welding in particular, in the sense of DIN ISO 9001, is to be categorized as a so-called special process, in the manner in which this is well known from the publication “Fügetechnik, Schweistechnik” [“Joining Technology, Welding Technology”], DVS Publishers, ISBN 3-87155-786-2; page 328, 2004. Particularly critical are in this case the effects of oxide layers on the corresponding connective parts, the wear and tear of the electrodes as well as the non-option of a definitive, for example optical or electrical checking of the connection.
The connection of such a conductor structure order of three elements with cross-sections respectively at variance with each other at the connection points is supposed to enable a long lifetime of approx. 10-15 years for example, so that the process of the installation of the order structure of the conductors is to be carried out in a very sure manner. For reasons of electrical conductivity, corresponding current bars and/or order structures of the conductors are predominantly constructed out of copper material. Problems arise in this case both in the case of hard soldering as well as in the case of welding in particular from the heating at the time of the creation of the connection points, as the heat is conducted by the conductor to the current transformer and can damage it.
The so-called cold press welding is generally known for the joining of tow metals, something which is for example described in the overview of the status and developmental tendencies of cold press welding, J. Ruge, H. Preis and K. Thomas, Braunschweig, DVS Report, volume 139, “Abbrennstumpfschweissen und Reibschweissen mit verwandten Verfahren” [“Flash welding and friction welding with related methods”], page 25, 1991. From the research report “Untersuchung zum ultraschall-gestützten KaltpressSchweissen für Anwendungen in der Kleinteilfertigung” [“Investigation of ultra-sound supported cold press welding for application in the manufacture of small parts”], Institut fur Schweisstechnik TU [Institute of Welding Technology, Technical University] Braunschweig, Institut für Füge- und Strahltechnik [Institute of Joining- and Jet Technology] Otto von Guericke, University of Magdeburg, AiF no. 12494 BG/4 Jun. 1, 2000/Sep. 30, 2002 and from “Informationen und Anwedungshinweise zur Tox-Verbindungstechnik” [“Information and application details for the Tox Joining Technology”] of the firm Tox-Pressotechnik GmbH & Co. KG, Weingarten, a clinching is known as a kind of clinch sealing of two metallic bodies.